Just go ahead and project, seek out some portion of the projected image that contains the tones you want, and do a test on a small fragment of paper. There is seldom a need to test the entire image.
When I get a new box of paper, I often sacrifice one sheet to make some test pieces for this kind of thing. The test pieces get exposed developed, topped, fixed, washed, dried... before I draw any conclusions about exposure of the "real" prints.
You shouldn't have to waste hardly any paper at all- test strips can tell you almost everything you need.... before you do the real thing.